Electrowinning cells for the recovery of gold are well known and consist fundamentally of a tank in which a static sandwich arrangement of alternate electrically connected anode and cathode assemblies are located in a flow path between the electrolyte inlet to the tank and an outlet weir from the tank.
In use, in one form of electrowinning, a gold rich eluate is fed into the tank through its inlet to pass between the electrified anodes and cathodes in the tank and from the tank through its outlet. In doing so a gold rich sludge is electrolytically built up on the low adhesion material of the cathodes and in time gravity separates from the cathodes to settle in a sump or gold trap in the base of the tank from where it is periodically removed.
The cathodes in the cells generally consist of steel wool which is trapped between perforated sheets which are made from a suitable plastics material and the anodes each consist of a composite unit which is made up of stainless steel strips.
For security reasons, the cell tank is closed by a lockable lid.
Although electrowinning cells of the above type are reasonably efficient their gold recovery rate is slow and a large percentage of gold remains trapped in the cathode wool which necessitates regular removal of the cathodes from the tank for maximum gold recovery by means of a calcine or acid treatment process. The removal of the gold laden cathodes from the tank is labour intensive and poses severe gold theft security problems.